Musnad Ahmad 35:10

Abdullah ibn Ahmad said: I found in my father’s book, in his own handwriting: Sa’id—meaning Ibn Sulayman—narrated to us, ‘Abbad—meaning Ibn al-‘Awwam—narrated to us, from Sufyan ibn Husayn, from al-Zuhri, from Ayyub ibn Bashir al-Ansari, from Hakim ibn Hizam, that a man asked the Messenger of Allah, may Allah bless him and grant him peace, about charities: "Which of them is best?" He said: "Upon the relative who harbors enmity."